Mask registration during continuous photoetching of strip material

ABSTRACT

PRINTED CIRCUITS ARE MADE FROM A STRIP OF INSULATIVE MATERIAL HAVING METAL FILMS BONDED ON OPPOSITE SIDES THEREOF. HOLES ARE PUNCHED IN SUCCESSIVE SECTIONS OF THE STRIP TO RECEIVE COMPONENT LEADS OR TO PROVIDE A PATH FOR AN ELECTRICAL CONNECTION BETWEEN CIRCUITS ON OPPOSITE SIDES OF THE BOARD. THE METAL FILMS ARE COVERED WITH A RADIANT ENERGY SENSITIVE RESIST AND THE RESIST COVERED STRIP IS MOVED CONTINUOUSLY PAST A FIRST RADIANT ENERGY SOURCE ADJACENT A FIRST SIDE OF THE STRIP AND PAST A SECOND RADIANT ENERGY SOURCE ADJACENT THE SECOND SIDE OF THE STRIP. A PLURALITY OF INDIVIDUAL MASKS ARE BROUGHT INTO SUCCESSIVE ENGAGE MENT WITH THE FIRST SIDE OF THE STRIP SUCH THAT A SINGLE MASK IS IN REGISTRATION WITH EACH SECTION PASSES THE FIRST RADIANT ENERGY SOURCE. A SECOND PLURALITY OF INDIVIDUAL MASKS ARE BROUGHT INTO SUCCESSIVE ENGAGEMENT WITH THE SECOND SIDE OF THE STRIP SUCH THAT A SINGLE MASK IS IN REGISTRATION WITH EACH SECTION AS THE STRIP PASSES THE SECOND RADIANT ENERGY SOURCE. THE RESIST MATERIAL IS THEN DEVELOPED AND THE METAL COATING IS ETCHED TO PRODUCE THE DESIRED CIRCUIT PATTERN. ELECTRICAL CONNECTIONS MAY THEN BE FORMED THROUGH HOLES CONNECTING CIRCUIT PATTERNS ON OPPOSITE SIDES OF THE STRIP.

June 20, 1972 o. E. CAMPBELL EI'AL 3,671,243

- MASK REGISTRATION DURING CONTINUOUS PHOTOETCHING OF STRIP MATERIAL Filed Oct. 26, 1.970 8 Sheets-Sheet'l II o I T IJNVE'NTUFQE- J 5 D.E'.E'F1/77PBE'L.L.

e F7. HERE/5 55 Q 7% W7WZ June 20, 1972 n. E. CAMPBELL E'TAL 3,671,243

MASK REGISTRATION DURING CONTINUOUS PHOTOETCHING OF STRIP MATERIAL Filed Oct. 26, 1970 8 sheetssheetlz June 20, 1972 D. E. CAMPBELL EI'AL 3,671,243

MASK REGISTRATION DURING CONTINUOUS PHOTOETCHING I OF STRIP MATERIAL Flled Oct 26 L970 8 sheetssheet 5 June 20, 1972 o. E. CAMPBELL EI'AL 3,671,243

MASK REGISTRATION DURING CONTINUOUS PHOTOETCHING OF STRIP MATERIAL 8 Sheets- Sheet 4 Filed Oct. 26, 1970 D. E. CAMPBELL EI'AL June 20, 1972 MASK REGISTRATION DURING CONTINUOUS PHOTOETCHING v 0F STRIP MATERIAL Flled Oct 26 1970 8 Sheets-Sheet 5 June 20, 1972 n. E. CAMPBELL trAL 3,671,243

MASK REGISTRAT DUR coumwous PHOTOETCHING F ST MATERIAL Filed Oct. 26, 1970 v 8 sheets sheet s June 20, 1972 D. E. CAMPBELL ETTA]. 3,671,243

MASK REGISTRATION DURING CONTINUOUS PHOTOETCHING OF STRIP MATERIAL Filed om. 26, 1970 s sheets shoet 7 United States Patent O1 fice 3,671,243 Patented June 20, 1972 U.S. Cl. 96-362 3 Claims ABSTRACT OF THE DISCLOSURE Printed circuits are made from a strip of insulative material having metal films bonded on opposite sides thereof. Holes are punched in successive sections of the strip to receive component leads or to provide a path for an electrical connection between circuits on opposite sides of the board. The metal films are covered with a radian-t energy sensitive resist and the resist covered strip is moved continuously past a first radiant energy source adjacent a first side of the strip and past a second radiant energy source adjacent the second side of the strip. A plurality of individual masks are brought into successive engagement with the first side of the strip such that a single mask is in registration with each section as the section passes the first radiant energy source. A second plurality of individual masks are brought into successive engagement with the second side of the strip such that a single mask is in registration with each section as the strip passes the second radiant energy source. The resist material is then developed and the metal coating is etched to produce the desired circuit pattern. Electrical connections may then be formed through holes connecting circuit patterns on opposite sides of the strip.

RELATED APPLICATION Application Ser. No. 80,365 entitled Apparatus for Conveying and Exposing A Strip of Radiant Energy Sensitive Material filed on Oct. 13, 1970 by Mr. R. A. Harris and assigned to Western Electric Company, Incorporated relates to making printed circuit boards which may be used in practicing the method of this invention.

BACKGROUND OF THE INVENTION (1) Field of the invention This invention relates to an improvement in a process for making printed circuit patterns on a metal coated strip of insulative material, and particularly, relates to a process wherein the metal coated strip is covered with a radiant energy sensitive resist which is exposed to radiant energy through a mask to produce the circuit patterns. In one such process the radiant energy sensitive resist is exposed to radiant energy through a mask which allows the radiant energy to pass to only selected areas of the resist. The resist is then developed leaving a resist pattern on the selected area. The metal coating not covered by the resist is etched away to produce a circuit pattern beneath the resist pattern. In an alternate process, the radiant energy is blocked by the mask from selected areas of the resist and after developing, the selected areas of metal not covered by resist are plated with an etch resistant metal or alloy, such as solder. The resist is then removed and the nonplated metal coating is etched away leaving a circuit pattern.

Holes are formed through the strip before the circuit patterns are formed thereon so that component leads may be inserted or electrical connections may be formed through the holes to connect circuit patterns on opposite sides of the strip. These holes must be accurately aligned with the circuit patterns.

(2) Prior art There are a number of prior art processes for making printed circuit patterns where radiant energy sensitive resist is exposed to radiant energy through a master or a mask. One such prior art process utilizes a transparent drum with a. mask mounted on the periphery of the drum. In this process the mask cannot be accurately aligned with the holes in the strip since the holes punched in successive sections of the strip often are not uniform in alignment with adjacent sections.

In another prior art process a section of strip is advanced into a printing station where the strip is stopped and forced by vacuum or pressure differential against a mask in registration with the mask and a radiant energy source exposes the strip through the mask. This prior art process is slow and requires a considerable amount of operator time.

SUMMARY OF THE INVENTION An object of the present invention is a new and improved process for making printed circuit patterns on a metal coated strip of insulative material.

Another object of the invention is a process of making printed circuits wherein masks are brought into accurate registration with corresponding sections of a radiant energy sensitive strip as it moves continuously past a radiant energy source.

In accordance with these and other objects, a process employing the principles of the invention contemplates forming a plurality of holes in successive sections of a metal coated insulative strip wherein there is formed at least two holes in the pattern for registration purposes. The metal coating is then covered with a radiant energy sensitive resist material and the strip is moved continuously past a radiant energy source. A mask is brought into registration with the holes in each section of the strip such that the mask moves with the strip as it passes the radiant energy source. The resist material is then developed and the metal coating is etched to produce the desired circuit patterns.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a cut away portion of a metal clad insulative strip used in the manufacture of printed circuits;

FIG. 2 illustrates a punch and die arrangement for producing a pattern of holes in successive sections of a strip;

FIG. 3 is a view of holes punched in successive sections of a strip by the apparatus shown in FIG. 2;

FIG. 4 illustrates an apparatus for applying a radiant energy sensitive material or covering to the surfaces of a strip;

FIG. 4A shows a cut away portion of a metal clad insulative strip with radiant energy sensitive material covering portions of the metal surfaces of the strip;

FIG. 5 illustrates an apparatus for conveying a strip through a work station, and particularly, for conveying a radiant energy sensitive strip through a beam of actinic radiant energy with a mask between the radiant energy source and the strip;

FIG. 6 is a pictorial drawing of some of the apparatus shown in FIG. illustrating in more detail various features of the apparatus;

FIG. 7 is a pictorial drawing of a carriage which rolls on tracks of the apparatus shown in FIGS. 5 and 6;

FIG. 8 is a pictorial drawing of a mask which is mounted on the carriage shown in FIG. 7;

FIG. 9 is a top view of an alternate overlay which may be used in place of the overlay shown in FIG. 8;

FIG. 10 shows a cut away portion of a flexible belt used in the apparatus of FIGS. 5' and 6 for forcing the strip of material against the mask on the carriages and moving the carriages and strip past the radiant energy source;

FIG. 11 illustrates an arrangement of driving chains and clutches for operating the apparatus of FIGS. 5 and 6;

FIG. 12 shows a housing for a radiant energy source which may be utilized in the apparatus of FIGS. 5 and 6;

FIG. 13 shows a rocking guide roller which may be utilized to aid in guiding the strip in registration with pins on the masks of the apparatus of FIGS. 5 and 6;

FIG. 14 illustrates a roller press assembly for the apparatus shown in FIGS. 5 and 6 for pressing the resilient belt tightly against the strip of material; and

FIG. 15 illustrates a slack sensing mechanim for controlling the advancement of the strip of material through the forward and rear sections of the apparatus shown in FIGS. 5 and 6 to insure the material is properly fed to each of the sections.

DETAILED DESCRIPTION Referring to FIG. 1 there is shown a section of strip which has an insulative film 21, such as flexible epoxy film, which is covered with a layer of metal 22 on the top thereof and a layer of metal 23 on the bottom thereof to form a laminate structure. The metal layers 22 and 23 may be copper foils which are bonded to the film 21 for use in the manufacture of printed circuits. Many varieties of such metal coated insulative strips are commercially available and may be purchased in rolls.

Referring now to FIG. 2, the strip 20 is advanced from a supply roll 26 between a punch 27 and a die 28 by an indexing wheel 29. The punch 27 is closed with the die 28 to produce a pattern of holes in succeeding sections 31a, 31b, and 310 of the strip as shown in FIG. 3. Suitable facilities (not shown) are provided for automatically advancing the indexing wheel through a predetermined angle to successively place the sections of the strip 20 between the punch 27 and die 28. The punched strip 20 is then wound on the take-up roll 30. As shown in FIG. 3, the punch 27 forms a plurality of holes 32-32 along the edges of each section of the strip 20 for registration purposes. A plurality of holes 33-33 are formed in each section to accommodate the leads of components or to be used as a path for a through-hole connection between circuit patterns on the upper and lower surfaces of the strip 20. The apparatus for indexing and forming the holes 32-32 and 33-33 in the strip cannot accurately form the holes in each section in alignment with the holes in adjacent sections. Also, the distance between adjoining sections varies considerably. Thus, the distance between sections 31a and 31b is different from the distance between 31b and 310. Also, the holes 32 in the section 31b are not aligned with the holes 32 formed in the adjoining sections 31a and 31c.

After punching holes through the strip 20, the metal surface areas where circuit patterns are to be made on the strip 20 are covered with a radiant energy sensitive resist material. The resist material may be a silver halide emulsion which is sprayed, dipped, or otherwise coated on the surfaces of the strip 20 or the resist material may be a photopolymerizable monomer. In FIG. 4 there is shown an apparatus for applying one type of photopolymerizable monomer material to the upper and lower surfaces of the strip 20. The strip 20 is fed from a supply roll 35 between a pair of pressing rollers 36 and 37 to a take-up roll 44. Strips of photopolymerizable monomer are fed from rolls 38 and 39 and bonded to the respective upper and lower surface of the strip 20. The photopolymerizable strips from the rolls 38 and 39 and has respective transparent support films 40a and 41a upon which layers 40b and 41b of photopolymerizable monomer emulsion are deposited. Cover films 42 and 43 are removed and wound on rolls 44 and 45 prior to the rollers 36 and 37 pressing the respective layers 40b and 4111 on support films 40a and 41a against the metal surfaces 22 and 23. A sandwich structure or strip 20a, shown in FIG. 4A, is produced, wherein the layers 40b and 41b of photopolymerizable monomer emulsion cover and firmly adhere to the metal surface areas where printed circuit patterns are to be made. If the metal surfaces have been properly cleaned by conventional techniques, such as scrubbing with a pumice, the support films 40a and 41a may be removed, either before or after exposure of the strip 20a to actinic radiant energy, and the layers 40b and 41b remain firmly adhering to the respective metal layers 22 and 23. Suitable rolls of strips of photopolymerizable material are sold under the trademark Riston by Du Pont de Nemours & Company of Delaware and under the trademark Laminar by Dynachem Corporation of California. These materials polymerize when exposed to ultraviolet radiation and they may be developed in a suitable solution where the unpolymerized material is removed from the metal surfaces. The polymerized material which remains may be used as a resist to a metal etching solution or to a metal plating bath where an etch resistant metal is plated on the exposed metal surfaces.

Referring now to FIGS. 5 and 6 there is shown an apparatus for exposing the upper and lower radiant energy sensitive surfaces of the strip 20a to radiant energy through masks. The upper surface of the strip 20a is exposed to radiant energy from a source 24 through masks 86-86 mounted on carriages 48-48 rolling around a first arrangement of outwardly facing circular tracks 57-60 and inwardly facing circular tracks 81 and 82. The lower surface of the strip 20a is exposed to radiant energy from a source 25 through masks -125 mounted on carriages 117-117 rolling around a second arrangement of outwardly facing circular tracks 126-129 and inwardly facing circular tracks 134 and 135.

The supporting framework for the tracks 57-60, 81, 82, 126-129, 134 and 135 is illustrated in FIG. 6. The tracks 59 and 81 are mounted on an annular support 63, the tracks 57 is mounted on an annular support 61, the tracks 60 and 82 are mounted on an annular support 64, the track 58 is mounted on an annular support 62, the tracks 128 and 134 are mounted on an annular support 132, the track 126 is mounted on an annular support 130, the tracks 129 and 135 are mounted on an annular support 133, and the track 127 is mounted on an annular support 131. The annular supports 61, 63, and 132 are mounted on plates 67 and 68 which are supported above the floor on posts 70, 71 and 72. Similarly, the annular supports 62, 64, 131 and 133 are mounted on plates 65 and 66 which are supported above the floor by three posts similar to the posts 70, 71 and 72. The plates 65, 66, 67 and 68 are all connected together by cross members 73-73 and 74-74. Additionally, the framework has an upper plate 124, a lower plate 111 and side plates 211-214 mounted on the posts (70-72, etc.), and the plates 65-68 for supporting other parts of the apparatus.

The details of a carriage 48 are shown in FIG. 7. The carriage 48 has a frame 49 with wheels 50 and 51 rotatably mounted thereon for rolling along the respective outwardly facing tracks 57 and 58 (FIG. 6). Arms 52 and 53 extending from the frame 49 have respective wheels 54 and 55 mounted thereon for rolling along the outwardly facing tracks 59 and 60. Arms 75 and 76 are pivotally mounted at first ends on the arms 52 and 53 with springs 77 and 78 urging the arms 75 and 76 toward the arms 52 and 53. Wheels 79 and 80 rotatably mounted on second ends of the arms 75 and 76 roll along the inwardly facing tracks 81 and 82. The springs 77 and 78 provide sufficient bias to hold the carriage 48 on the tracks 57-60. A pair of arms 84 and 85 extend rearwardly to support the mask 86 which is attached to the arms 84 and 85 by threaded bolts 87 and 88 and pins 89 and 90. The bolts 87 and 88 have heads in recesses 91 and 92 of the mask 86, shown in (FIG. 8, to loosely secure the mask 86 to the arms 84 and 85. Shank portions of the bolts 87 and 88 extend through oblong holes 93 and 94 in the mask while the pins 89 and 90 extend into holes 95 and 96 formed through the masks 86. The holes 93-96 are made sufliciently larger than the shanks of the bolts 87 and 88 and the pins 89 and 90 so that the mask 86 may move in a horizontal plane relative to the frame 49 within predetermined limits.

As shown in FIG. 8, the mask 86 has a plurality of pins 98-98 for cooperating with the registration holes 32-32 that have been punched in the strip 20 as shown in FIG. 3. As previously mentioned, the apparatus for forming the holes shown in FIG. 2 cannot accurately align the holes in succeeding sections of the strip 20. The mask 86 is designed to have dimensions corresponding to a section 31a, 31b or 310 of the strip 20 and the freedom of movement of each carriage relative to the other carriages and the freedom of movement of each mask relative to its carriage assures that each mask is accurately aligned with the holes in a section of the strip even though adjoining sections may be separated by different distances and even though the holes formed in a section are not aligned with the adjacent sections.

Referring back to FIG. 7, arms 99 and 100 extend forward and slightly downward from the frame 49. The arms 99 and 100 have respective adjustable bolts 1'01 and 102 which abut with the back face of the arms 84 and 85 of the preceding adjacent carriage to prevent damage to the masks as the carriages roll over the uppermost portion of the tracks 57-60. Rollers 103 and 104 on the respective arms 99 and 100 support the rear end of the mask 86 of the preceding adjacent carriage.

Referring back to FIGS. and 6, the carriages 117-117 and masks 125-125 are similar to the carriages 48-48 and masks 86-86. The carriages 48-48 move in a counterclockwise direction while the carriages 1 17-117 move in a clockwise direction. The wheels and arms on the carriages 117-117 are reversed so that the wheels on the tracks 126 and 127 are the leading wheels, the same as the wheels 50 and 51 on the tracks 57 and 58 are the leading wheels. The tracks 134 and 135 are eccentric with the tracks 128 and 129. The springs biasing the arms upon which the wheels rollon tracks 128 and 129 are sufficiently strong to move the carriages against the force of gravity toward the point where the tracks 134 and 135 are closest to the tracks 128 and 129. This moves the carriages 1-17-117 into position to receive the strip 20a from the first arrangement of carriages 48-48.

Referring to FIGS. 5 and 6', the strip 20a passes over a rocking roller 47 and is forced by a driven flexible belt 105 moving on rollers 106-109 with the rollers 106, 107 and 109 rotatably mounted on the plates 211 and 212 to force the strip 20a against the masks 86-86 on the carriages 48-48. One end of the roller 108 is rotatably mounted on one end of an arm 110 which is pivotally mounted at a second end on the bottom plate 111. A piston rod 112 and an air cylinder 113 connected between the bottom plate 111 and the second end of the arm 110 pivots the arm 110 to tighten or loosen the belt 105. A similar arm, piston rod and air cylinder arrangement (not shown) simultaneously operated with the air cylinder 113 supports the other end of the roller 108. The roller 109 is driven as hereinafter described.

Referring to FIG. 10, the belt 105 has an inner layer 115 which is a conventional corded belting material. The outer surface of the belting material 115 is covered with a sponge or soft resilient rubber-like material 11 6 which is formed into a wafile grid structure. The soft resilient material 116 presses the strip 20a. firmly and evenly against the surface of the mask 86.

Referring back to FIG. 5, the strip 20a is forced by a driven belt 118 against the masks on the carriages 117. The belt 118 is similar to the belt 105 and is mounted on rollers 119-122 with the rollers 119, 120 and 122 rotatably mounted on the plates 213 and 214. One end of the roller 121 is mounted on an arm 123 pivoted on the upper plate 124 by an air cylinder 143 to select the tension on the belt 118. A similar arrangement (not shown) of an arm, piston rod and air cylinder supports the other end of the roller.

Referring to FIG. 8, there is shown one method of placing a pattern on the masks 86. The mask 86 has a plate which is made of a glass or plastic which is transparent to the radiant energy used to expose the strip 20a. The registration pins 98-98 are embedded in the plate 140. An overlay 141, such as a photographic negative or the like, is placed over the plate 140 on the registration pins 98-98. The overlay 141 in FIG. 8 has an opaque background with the desired circuits transparent. As shown in FIG. 9, an alternate overlay 142 has a circuit pattern defined by an opaque image with the surrounding area transparent. The overlay 141 may be used in a process wherein the developed resist is used as a resist to the metal etching solution whereas the overlay 142 may be used in a process where an etch resistant alloy is plated on the bared metal surfaces in the developed resist pattern.

Referring to FIG. 11 there is shown a motor for driving a chain sprocket 151 upon which chains 152-154 run. The chain 152 passes over a sprocket 155 which is connected by a clutch 156 to the roller 109 (FIGS. 5 and 6) and a sprocket 157 which is connected by a clutch 158 to the roller 1'19 (FIGS. 5 and 6). The chain 153 passes over a sprocket 159 connected by a clutch 160 to the supply reel 46 (FIG. 5). Similarly, the chain 154 passes over a sprocket 161 connected by a clutch 162 to the take-up reel 163 (FIG. 5).

Referring to FIG. 15 there is shown an apparatus for controlling the slack of the strip 20a between the first arrangement of carriages 48-48, and the second arrangement of carriages 117-117. The apparatus has a pair of shafts .164 and 165 which are rotatably mounted in the framework of the machine. Members 166 and '167 mounted on the ends of shafts 164 and 165 have a pair of bars 168 and 169 which support respective guide members 170-170 and 171-171 thereon. As shown in FIG. 5, the strip 20a loops between the guides 170-170 and 171-171 such that when there is too much slack in the strip 20a the bars 164 and 165 are rotated clockwise; and if there is not enough slack in the strip 20a, the bars 164 and 165 are rotated counterclockwise. An arm 172 mounted on the shaft 165 extends between two microswitches 173 and 174 such that clockwise rotation of shaft 165 actuates switch 173 and counterclockwise rotation of shaft 165 actuates switch 174. A weight 175 mounted on the shaft 164 normally maintains the arm 172 in a neutral position between the microswitches 173 and 174. When there is too much slack in the strip 20,

the arm 172 engages the microswitch 173 to operate the clutch 156 (FIG. 11) to disconnect the drive to the roller 109 and belt 105 (FIG. until the belt 118 takes up the slack to release the arm 172 from engagement from the microswitch 173. Similarly, if there is insufficient slack in the strip 20, the microswitch 174 is actuated to operate the clutch 158 to disconnect the drive to the roller 119 and belt 118 until the belt 105 again supplies additional slack.

Referring to FIG. 5 there is shown a proximity switch '176 beneath a loop extending from the supply roll 46. The proximity switch operates the clutch 160 (FIG. M) to maintain a predetermined amount of slack in the strip 20a. Similarly, a proximity switch 177 beneath a loop in the strip 20a next to a take-up reel 163 operates the clutch 162 (FIG. 11) to maintain a predetermined slack in the strip 20a. The proximity switches 176 and 177 are a conventional design.

Referring to FIG. 13 there is shown the support for the rocking roller 47. The roller 47 has a pair of ball joints 178 and 179 which are mounted on a pair of arms 180 and 181 pivotally connected to the plates 6568 of the apparatus shown in FIG. 6. An arm 182 extending from the plate 65 has an air cylinder 183 pivotally mounted thereon with a piston rod 184 pivotally connected to the arm 180. An oscillating air supply is connected to the air cylinder 183 to oscillate the roller 47 from side to side. The motion of the roller 47 insures that the holes 32 on the strip 20a register with the pins 98 on the masks 86.

Referring to FIG. 12 there is shown a lamp housing assembly for supplying a beam of radiant energy to expose the top surface of the strip 20a. The assembly has a member 186 mounted on the cross members 73-73 (FIG. 6) with a screw 187 threaded through the member 186. Bars .188 and 18 9 are slidable in suitable grooves in the member 186. The screw 1-87 is supported against longitudinal movement for rotation by a cross member 190 extending between the bars 188 and 189 and a suitable bearing 198 on a lamp enclosure 1'92 mounted on the lower ends of the bars 188 and 18 9'. A motor 191 mounted on the member 190 is utilized to drive the screw 187 to move the bars 188 and 1 89 upward and downward relative to the member 186. The lamp enclosure 192 contains a suitable ultraviolet lamp, a reflector, a collimator, a cooling fan, and such other facilities necessary for the production of the proper intensity of radiant energy necessary to expose the strip 20a. Arms 193 and 194 are pivotally mounted on the bars 188 and 189 and support a shutter 195 which may be moved by an air cylinder 196 and a piston rod 197 into or away from the face of the lamp enclosure 192. Thus, the ultraviolet lamp source in the enclosure 192 may be closed off to prevent unwanted exposure of the strip 20a and to eliminate hazardous conditions to an operator. The enclosure 192 is selectively moved toward or away from the strip 20a by the motor 191 to obtain the optimum intensity of light exposing the light sensitive material strip 20a. A similar lamp housing assembly (not shown) is mounted on the cross members 74-74 (FIG. 6) with the lamp enclosure face upward to expose the bottom surface of the strip 20a.

Referring to FIG. '14, there is shown a belt press assembly having a pair of side members 199 and 200 which are supported in the framework for engaging the belt 105 to provide additional pressure on the belt forcing the upper surface of the strip 20a against the masks 8686. The belt press member has a plurality of rollers 201-203 mounted on respective pairs of arms 204-206 which are pivoted on the members 19 9 and 200. Springs 207-209 are attached to bars 210-2112 mounted on the arms 202204 and the members 1 99 and 200 to urge the rollers 201-203 upward against the belt as shown in FIG. 5. A similar belt press assembly (not shown) is provided for pressing the belt 118 and lower surface of the strip 20a against the masks 125125.

After the resist layers 40b and 41b have been selectively exposed to radiant energy, the resist is developed and the circuits are formed in a conventional manner such as by etching, or by plating an etch resistant metal or alloy and then etching. Electrical connections may be made through selected holes between circuit patterns on opposite sides of the film 21 by conventional techniques such as electroless plating of copper followed by electrolytic plating of copper. The forming of connections through the holes may be made at any time or step after the holes have been punched. Forming of additional resist coatings may be necessary for the forming of connections through the holes, or the resist layers 40b and 4112 may be used prior to forming and etching the circuit patterns.

It is to be understood that the above-described embodiments are simply illustrative of the principles of the invention and that many other embodiments may be devised without departing from the scope and spirit of the invention.

What is claimed is:

1. A method of making electrical circuit patterns on a first side of an insulative strip having a layer of metal coated on the first side thereof, comprising:

forming a pattern of holes in successive sections of the strip including at least two holes in each pattern for registration purposes;

covering the metal coating on the first side with a radiant energy sensitive resist material;

moving the strip continuously past a radiant energy source adjacent the first side of the strip;

bringing a plurality of separate individual masks, each having registration means adapted to cooperate with the registration holes in each section of the strip, into successive engagement with the first side of the strip such that each mask is in registration with the holes in each section of the strip as that section passes the radiant energy source;

developing the resist material; and

etching the metal coating to produce the desired circuit patterns.

2. A method of making electrical circuit patterns on first and second sides of an insulative strip having layers of metal coated on the first and second sides comprising:

forming a pattern of holes in successive sections of the strip including at least two holes in each pattern for registration purposes; covering the metal coatings on both the first and second sides with a radiant energy sensitive resist material;

moving the strip continuously past a radiant energy source adjacent the first side of the strip and past a radiant energy source adjacent the second side of the strip;

bringing a first plurality of separate individual masks,

each having registration means adapted to cooperate with the registration holes in each section of the strip, into successive engagement with the first side of the strip such that each mask of the first plurality is in registration with each section as that section passes the radiant energy source adjacent the first side;

bringing a second plurality of separate individual masks,

each having registration means adapted to cooperate with the registration holes in each section of the strip, into successive engagement with the second side of the strip such that each mask of the second plurality is in registration with each section as that section passes the radiant energy source adjacent the second side;

developing the resist material; and

etching the metal coating to produce the desired circuit patterns.

3. A method as defined in claim 2, wherein at least one hole is formed in each section for making a through-hole connection between the first and second sides of the strip 9 10 and which includes the additional step of forming an 3,298,297 1/1967 Carlson et a1. 355111 electrical connection between circuit patterns on the first 2,977,867 4/1961 Woodworth 355111 and second sides through the one hole for making a 2,556,930 6/1951 Miller 355104 through-hole connection. 2,552,255 5/ 1951 Capstatf 355-111 5 2,041,478 5/1936 Niederle 355-109 References Cited G. Prlmary Exannner 3,578,862 5/1971 Hudock 61111. 355-404 WINKELMAN, AssistantExaminer 3,415,699 12/1968 Brown 96-36 10 US. 01. X.R. 3,313,225 4/1967 Mears 3ss s9 35589:103,109 

